apparmor: fix out-of-bounds write when null terminating a label vec

Overview

In the Linux kernel, the following vulnerability has been resolved:

apparmor: fix out-of-bounds write when null terminating a label vec

aa_vec_unique() null terminates at vec[n - dups] when VEC_FLAG_TERMINATE is passed. If the components are all distinct no duplicates are dropped, dups is 0 and the terminator goes to vec[n], so the caller has to provide room for n + 1 entries.

aa_label_strn_parse() sets up its vector with vec_setup(profile, vec, len, gfp) and then calls aa_vec_unique(vec, len, VEC_FLAG_TERMINATE), but vec_setup() does not reserve the terminator entry. Up to LOCAL_VEC_ENTRIES it uses the local array of LOCAL_VEC_ENTRIES pointers, above that it allocates exactly len pointers. The terminator therefore lands one entry past the end of the local array when len is LOCAL_VEC_ENTRIES, and one entry past the end of the allocation when len is larger.

len comes from the number of "//&" separated components in the label name and label_count_strn_entries() does not bound it. An unprivileged task reaches the parse by writing to /proc/self/attr/apparmor/current or through lsm_set_self_attr(2), both of which go through do_setattr(), and the name is parsed before the change_profile permission is checked. The query_label() path behind the securityfs .access file, which is mode 0666, performs no permission check at all. Every component has to resolve to a loaded profile, so a system with policy loaded is required.

The other two VEC_FLAG_TERMINATE users work on a label vec that aa_label_alloc() has already sized with "+ 1 for null terminator entry on vec". Reserve the same entry in vec_setup() and DEFINE_VEC(). Passing len + 1 from the caller instead would move len == LOCAL_VEC_ENTRIES out of the local array and into kzalloc().

Affected

• Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < b17c8f5dcb36a032688847b2bce4bd813b4baad1
• Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 9124e078ea2250d8d01d2162a550acb01ef5bf48
• Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 28069434aef66b9d084f0609b7a29c171846815e
• Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 36bdd0b45ec3f4822832a56e9db8674c8450dfce
• Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 9f1e40193eef7f047e6b77cfb4b4cafdecd7a123
• Linux 4.13

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · updated 2026-09-21 · vex